/*********************************************************************************
 *      Copyright:  (C) 2025 LingYun<lingyun@email.com>
 *                  All rights reserved.
 *
 *       Filename:  signal.c
 *    Description:  This file 
 *                 
 *        Version:  1.0.0(17/03/25)
 *         Author:  LingYun <lingyun@email.com>
 *      ChangeLog:  1, Release initial version on "17/03/25 20:52:50"
 *                 
 ********************************************************************************/

#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <signal.h>

int g_child_stop = 0;
int g_parent_run = 0;

void sig_child(int signum)
{
	if(SIGUSR1 == signum)
	{
		g_child_stop = 1;
	}
}

void sig_parent(int signum)
{
	if( SIGUSR2 == signum)
	{
		g_parent_run = 1;
	}
}

int main(int argc, int **argv)
{
	int			pid;
	int			wstatus;

	signal(SIGUSR1, sig_child);
	signal(SIGUSR2, sig_parent);

	if((pid =fork()) < 0)
	{
		printf("Create child process failure: %s \n",strerror(errno));
		return -2;
	}
	else if(pid == 0)
	{
		/* child process can do something first here, then tell parent process to start running*/
		printf("Child process start running and send parent a signal\n");
		kill(getppid(),SIGUSR2);

		while(! g_child_stop )
		{
			sleep(1);
		}

		printf("Child process receive sognal from parent and exit now\n");
		return 0;
	}

	printf("Parent hangs up unrill receive signal from child!\n");
	while(!g_parent_run)
	{
		sleep(1);
	}

	/* parent process can do something here ,then tell child process to exit */

	printf("Parent start running now and send child a signal to exit\n");
	kill(pid,SIGUSR1);

	/* parent wait child process exit */
	wait(&wstatus);
	printf("Parent wait child process die and exit now\n");

	return 0;
}
